POSTERIOR PART OF LOWER EXTREMITY. 



Dissection. Locate greater trochanter, sacrum, coccyx, tuber of ischium, 

 crest of. ilium, inner and' outer hamstrings, head of fibula, neck of fibula, os calcis, 

 inner and outer malleoli. 



Incisions. (i) From centre of crest of ilium to centre of the os calcis ; (2) 

 from greater trochanter to coccyx ; (3) from internal to external condyle ; 

 (4) from inner malleolus to outer malleolus. Cut deeply enough to permit the 

 edges of the skin to separate one-half of an inch with ease. In removing the 

 skin from any area, cut closely enough that light may shine through the skin. 

 The thing you see now having removed the skin is the superficial fascia. It 

 contains the following structures in a variable amount of fat (Fig. 255) : 



Cutaneous or sensory nerves in figure 255. 



1 . TIic twelfth or last thoracic nerve below the twelfth rib. 



2 . The iliac brancJi of the ilio-liypogastric nerve. 



3 . Posterior branches of the lumbar and sacral nerves. 



4. The external cutaneous nerve of the lumbar plexus. 



5. Tlie small sciatic of the sacral plexus. 



6. The cutaneous branch of the obturator nerve. 



7. Twigs from the long or internal saphenous. 



8. The short saphenous, formed, as you see in figure 255, by the communicans 

 tibialis and communicans fibularis, branches of internal and external popliteal 

 respectively. 



9. The short saphenous vein, with the nerve described in the preceding para- 

 graph. This vein comes from the outer end of the dorsal arch of the foot, runs 

 behind the outer malleolus of the fibula, passes up the mid-line of the leg, 

 between the two heads of the gastrocnemius muscle, pierces the deep popliteal 

 fascia, and opens into the popliteal vein. 



Describe the twelfth thoracic nerve. 



It is seen giving (i) a cutaneous branch to the anterior part of the gluteal 

 region ; (2) a cutaneous branch to the anterior part of the abdominal walls as low 

 as the hypogastric region. The nerve lies below the last rib, with the first lumbar 

 artery. It crosses the quadratus lumborum muscle, and its muscular branches 

 are distributed like the other abdominal intercostals. 



Describe the ilio- hypogastric nerve. 



This is a branch of the lumbar plexus, being given off from the first lumbar 

 with the ilio-inguinal nerve. The iliac branch supplies the integument of the 

 front part of the gluteal region. The hypogastric branch pierces the aponeurosis 

 of the external oblique muscle one inch above the external abdominal ring, and 

 supplies the skin in this region. 



Observe that the posterior branches of the lumbar and sacral nerves supply 

 the skin over the glutens maximus muscle. 



Remember, the external cutaneous branch of the lumbar plexus supplies the 

 skin covering the vastus externus, and may be considered a dismembered branch 

 of the anterior crural nerve, according to Hilton's law. 



365 



